Neuromodulation of cortico-mesolimbic dopamine (CMDA) function may be more effective for the treatment of alcohol dependence than DA receptor blockade, and consistent with this hypothesis, we have shown that ondansetron a serotonin-3 antagonist that modulates CMDA primarily in the ventral tegmental area and nucleus accumbens (NAc), is efficacious treatment for a subtype of alcohol dependent humans with high biological loading for the disease. We have also demonstrated that topiramate, a GABA/glutamate (GLU) modulator that is believe to produce widespread suppression of CMDA, is an efficacious treatment for a heterogeneous group of alcohol dependent individuals. Because ondansetron and topiramate manifest their effects through different neuronal processes, both resulting in modulation of CMDA function, it is reasonable to hypothesize that their combination shall be more efficacious than either alone in the treatment of alcohol dependence. Therefore, we propose to characterize the mechanistic process by which ondansetron and topiramate, both alone and in combination, exert their behavioral and neurochemical effects using different rat self-administration models and strains. In Aim 1 and 2 we will examine the prediction that both ondansetron and topiramate alone and in combination will reduce ethanol reinforcement, and in Aim 2 and 3 we will examine the prediction that both ondansetron and topiramate alone and in combination will reduce ethanol reinstatement. The combination is expected to be associated with added or synergistic decreases in ethanol reinforcement and reinstatement as well as associated modulation in CMDA and GLU concentrations. This pharmaco-behavioral response pattern or finger-print will enable us to identify future promising putative medications with similar effects as well as enable us to understand which of their properties can be harnessed to develop even more potent medications. PUBLIC HEALTH RELEVANCE Our study is significant because it focuses on determining the biological basis for the effects of two potential medications, ondansetron and topiramate, for treating alcohol dependence. The overall goals of this basic science work is to helping to identify populations that may be ideally suited for treating alcohol dependence with these two medications, and to provide information that may guide the development of even more effective medications.